对于linkedlist你了解多少呢?下面要给大家介绍的就是linkedlist类的特点方面的内容，一起来对linkedlist进行一下了解吧。
linkedlist具有以下的几个特点：
1、null值：它可以有多个null值
2、数据重复性：数据是可以重复的
3、数据有序性：保证了插入数据的有序性
底层数据结构
private static class Node < E >
{
E item;
Node < E > next;
Node < E > prev;
Node(Node < E > prev, E element, Node < E > next)
{
this.item = element;
this.next = next;
this.prev = prev;
}
}linkedlist底层提供的是双向链表
继承关系
public class LinkedList < E > extends AbstractSequentialList < E > implements List < E > , Deque < E > , Cloneable, java.io.Serializable
{}linkedlist继承了AbstractSequentialList类，它继承了AbstractList类。
linkedlist实现了List接口，Deque接口。
能够克隆，能够进行反序列化以及序列化操作。
基本属性
transient int size = 0; //表示当前集合存储数据个数 transient Node < E > first; //第一个节点 transient Node < E > last; //最后一个节点 private static final long serialVersionUID = 876323262645176354 L; //用于Java的序列化机制 protected transient int modCount = 0; //表示的是版本控制，添加，删除，修改之类的操作都会进行++操作
构造函数
//无参构造函数，构造出一个空列表
public LinkedList()
{}
//使用集合的构造方法，先构造出一个空列表，之后，再将集合当中所有元素添加到列表里面
public LinkedList(Collection < ? extends E > c)
{
this();
addAll(c);
}主要的实现方式
//头插法插入指定结点
private void linkFirst(E e)
{
final Node < E > f = first;
final Node < E > newNode = new Node < > (null, e, f);
first = newNode;
if (f == null)
last = newNode;
else
f.prev = newNode;
size++;
modCount++;
}
//尾插法插入指定结点
void linkLast(E e)
{
final Node < E > l = last;
final Node < E > newNode = new Node < > (l, e, null);
last = newNode;
if (l == null)
first = newNode;
else
l.next = newNode;
size++;
modCount++;
}
//将指定结点插入到指定节点之前
void linkBefore(E e, Node < E > succ)
{
final Node < E > pred = succ.prev;
final Node < E > newNode = new Node < > (pred, e, succ);
succ.prev = newNode;
if (pred == null)
first = newNode;
else
pred.next = newNode;
size++;
modCount++;
}
//头删法删除结点
private E unlinkFirst(Node < E > f)
{
final E element = f.item;
final Node < E > next = f.next;
f.item = null;
f.next = null;
first = next;
if (next == null)
last = null;
else
next.prev = null;
size--;
modCount++;
return element;
}
//尾删法删除结点
private E unlinkLast(Node < E > l)
{
final E element = l.item;
final Node < E > prev = l.prev;
l.item = null;
l.prev = null;
last = prev;
if (prev == null)
first = null;
else
prev.next = null;
size--;
modCount++;
return element;
}
//删除指定结点
E unlink(Node < E > x)
{
final E element = x.item;
final Node < E > next = x.next;
final Node < E > prev = x.prev;
if (prev == null)
{
first = next;
}
else
{
prev.next = next;
x.prev = null;
}
if (next == null)
{
last = prev;
}
else
{
next.prev = prev;
x.next = null;
}
x.item = null;
size--;
modCount++;
return element;
}
//返回此列表的第一个元素
public E getFirst()
{
final Node < E > f = first;
if (f == null)
throw new NoSuchElementException();
return f.item;
}
//返回此列表的最后一个元素
public E getLast()
{
final Node < E > l = last;
if (l == null)
throw new NoSuchElementException();
return l.item;
}
//头删法删除结点
public E remove()
{
return removeFirst();
}
//移除此列表中指定位置处的元素
public E remove(int index)
{
checkElementIndex(index);
return unlink(node(index));
}
//移除并返回此列表的第一个元素
public E removeFirst()
{
final Node < E > f = first;
if (f == null)
throw new NoSuchElementException();
return unlinkFirst(f);
}
//移除并返回此列表的最后一个元素
public E removeLast()
{
final Node < E > l = last;
if (l == null)
throw new NoSuchElementException();
return unlinkLast(l);
}
//删除指定元素
public boolean remove(Object o)
{
if (o == null)
{
for (Node < E > x = first; x != null; x = x.next)
{
if (x.item == null)
{
unlink(x);
return true;
}
}
}
else
{
for (Node < E > x = first; x != null; x = x.next)
{
if (o.equals(x.item))
{
unlink(x);
return true;
}
}
}
return false;
}
//从此列表中移除所有元素
public void clear()
{
for (Node < E > x = first; x != null;)
{
Node < E > next = x.next;
x.item = null;
x.next = null;
x.prev = null;
x = next;
}
first = last = null;
size = 0;
modCount++;
}
//将给定元素插入此列表的开头
public void addFirst(E e)
{
linkFirst(e);
}
//将给定元素追加到此列表的结尾
public void addLast(E e)
{
linkLast(e);
}
//判断此列表是否包含指定元素
public boolean contains(Object o)
{
return indexOf(o) != -1;
}
//返回此列表的元素数
public int size()
{
return size;
}
//尾插法插入指定结点
public boolean add(E e)
{
linkLast(e);
return true;
}
//返回此列表中指定位置处的元素
public E get(int index)
{
checkElementIndex(index);
return node(index)
.item;
}
//将此列表中指定位置的元素替换为指定的元素
public E set(int index, E element)
{
checkElementIndex(index);
Node < E > x = node(index);
E oldVal = x.item;
x.item = element;
return oldVal;
}
//将指定集合中所有元素添加到指定集合的后面
public boolean addAll(Collection < ? extends E > c)
{
return addAll(size, c);
}
//在指定位置插入指定集合
public boolean addAll(int index, Collection < ? extends E > c)
{
checkPositionIndex(index);
Object[] a = c.toArray();
int numNew = a.length;
if (numNew == 0)
return false;
Node < E > pred, succ;
if (index == size)
{
succ = null;
pred = last;
}
else
{
succ = node(index);
pred = succ.prev;
}
for (Object o: a)
{
Node < E > newNode = new Node < > (pred, e, null);
if (pred == null)
first = newNode;
else
pred.next = newNode;
pred = newNode;
}
if (succ == null)
{
last = pred;
}
else
{
pred.next = succ;
succ.prev = pred;
}
size += numNew;
modCount++;
return true;
}
//将指定元素插入到指定下标位置之前
public void add(int index, E element)
{
checkPositionIndex(index);
if (index == size)
linkLast(element);
else
linkBefore(element, node(index));
}
//判断下标是否合法
private boolean isElementIndex(int index)
{
return index >= 0 && index < size;
}
private boolean isPositionIndex(int index)
{
return index >= 0 && index <= size;
}
private void checkElementIndex(int index)
{
if (!isElementIndex(index))
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}
private void checkPositionIndex(int index)
{
if (!isPositionIndex(index))
throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}
//返回指定位置的结点
Node < E > node(int index)
{
if (index < (size >> 1))
{
Node < E > x = first;
for (int i = 0; i < index; i++)
x = x.next;
return x;
}
else
{
Node < E > x = last;
for (int i = size - 1; i > index; i--)
x = x.prev;
return x;
}
}
//返回指定元素第一次出现的下标
public int indexOf(Object o)
{
int index = 0;
if (o == null)
{
for (Node < E > x = first; x != null; x = x.next)
{
if (x.item == null)
return index;
index++;
}
}
else
{
for (Node < E > x = first; x != null; x = x.next)
{
if (o.equals(x.item))
return index;
index++;
}
}
return -1;
}
//返回指定元素最后一次出现的下标
public int lastIndexOf(Object o)
{
int index = size;
if (o == null)
{
for (Node < E > x = last; x != null; x = x.prev)
{
index--;
if (x.item == null)
return index;
}
}
else
{
for (Node < E > x = last; x != null; x = x.prev)
{
index--;
if (o.equals(x.item))
return index;
}
}
return -1;
}
public E peek()
{
final Node < E > f = first;
return (f == null) ? null : f.item;
}
public E element()
{
return getFirst();
}
public E poll()
{
final Node < E > f = first;
return (f == null) ? null : unlinkFirst(f);
}
public boolean offer(E e)
{
return add(e);
}
public boolean offerFirst(E e)
{
addFirst(e);
return true;
}
public boolean offerLast(E e)
{
addLast(e);
return true;
}
public E peekFirst()
{
final Node < E > f = first;
return (f == null) ? null : f.item;
}
public E peekLast()
{
final Node < E > l = last;
return (l == null) ? null : l.item;
}
public E pollFirst()
{
final Node < E > f = first;
return (f == null) ? null : unlinkFirst(f);
}
public E pollLast()
{
final Node < E > l = last;
return (l == null) ? null : unlinkLast(l);
}
public void push(E e)
{
addFirst(e);
}
public E pop()
{
return removeFirst();
}
//返回ListIterator迭代器
public ListIterator < E > listIterator(int index)
{
checkPositionIndex(index);
return new ListItr(index);
}
//返回Iterator迭代器
public Iterator < E > descendingIterator()
{
return new DescendingIterator();
}
//返回此 LinkedList 的浅表复制
public Object clone()
{
LinkedList < E > clone = superClone();
clone.first = clone.last = null;
clone.size = 0;
clone.modCount = 0;
for (Node < E > x = first; x != null; x = x.next)
clone.add(x.item);
return clone;
}
//以正确顺序返回包含此列表中所有元素的数组
public Object[] toArray()
{
Object[] result = new Object[size];
int i = 0;
for (Node < E > x = first; x != null; x = x.next)
result[i++] = x.item;
return result;
}
//以正确顺序返回包含此列表中所有元素的数组,返回数组的运行时类型即为指定数组的类型
public < T > T[] toArray(T[] a)
{
if (a.length < size)
a = (T[]) java.lang.reflect.Array.newInstance(a.getClass()
.getComponentType(), size);
int i = 0;
Object[] result = a;
for (Node < E > x = first; x != null; x = x.next)
result[i++] = x.item;
if (a.length > size)
a[size] = null;
return a;
}
//通过JAVA对象流进行序列化和反序列化
private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException
{
s.defaultWriteObject();
s.writeInt(size);
for (Node < E > x = first; x != null; x = x.next)
s.writeObject(x.item);
}
private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException
{
s.defaultReadObject();
int size = s.readInt();
for (int i = 0; i < size; i++)
linkLast((E) s.readObject());
}效率
增加和删除的效率比较高，查询和修改的效率比较的低。
那么关于linkedlist类的特点就简单的给大家介绍到这里了，假如你还想了解更多关于这方面的内容，请继续关注奇Q工具网的java入门栏目了解吧。
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